Some New Rhododendron Hybrids
By Benjamin Pecherer
After reading about the work of Dietrich Hobbie in the book "Rhododendrons", 1956 by The American Rhododendron Society, I became quite enthusiastic about the dense low growing plants with brilliant scarlet flowers and decided to see whether I could obtain some of them. I finally located Mr. Hobbie through the German Rhododendron Society and wrote to him. Mr. Hobbie turned out to be a most interesting and willing letter writer and an extremely prolific source of information about rhododendrons. During the course of our correspondence he told me that he was planning to visit the United States with a group of German nurserymen during the summer of 1956, and we made plans to meet in New York City.
On July 7, Mr. Joseph Casadevall and I met Mr. Hobbie at his hotel; we came equipped with a projector and screen, he had his slides. Without delay we started viewing the slides. For more than two hours we saw what could only be vaguely comprehended from his letters; he was apparently hybridizing on a scale unprecedented in the history of rhododendron breeding. The slides included an amazing variety of rhododendron hybrids. Tonight I shall show you some of the slides especially those illustrating the hybrids based on R. williamsianum and R. forrestii var. repens .
First a few words about Mr. Hobbie, his location, and his objectives. He lives on a fairly large estate near the town of Linswege in northwest Germany, near Bremen and but a short distance from the borders of Holland. Generally the climate is described as maritime. The Encyclopedia Brittanica reports that the mean summer temperature of that region is sixty to sixty-two degrees, the winter temperatures average about thirty degrees, while the annual rainfall is somewhat in excess of thirty-four inches. By way of contrast Mr. Ralph H. Carver reported in the "Azalea Handbook" that in the neighborhood of Elizabeth, New Jersey, the winter temperature ranged from five degrees above zero to four degrees below zero with an average annual rainfall of fifty-one inches. Mr. Hobbie has written me that a very severe winter can be expected every six or seven years during which the temperature may drop to twenty below zero. In any case the temperature is equable, more or less uniform once it has changed. The nursery itself is located in a century-old pine forest. Mr. Hobbie first started growing rhododendron from seed about 1929. He received seeds of many species from the expeditions of Hu, Schafer, and Sherriff as well as from Mr. Joseph B. Gable and Professor W. W. Smith of Edinburgh. For about eight years the growing of the species was his main interest. In 1937 on a trip to England he visited the famous rhododendron gardens in that country and saw for the first time what the hybridizers had accomplished. On the spot a resolve to start hybridizing was born. As a start he planted F2 seeds of the exotic British hybrids, but after a few seasons he learned a lesson which was to be remembered in all future breeding work; beautiful though these hybrids were thy were far too tender for his location nor was there sufficient hardiness in their breeding to make likely the appearance of any hardy offspring. After a few seasons all of the seedlings were lost in a severe winter. As a result of such experiences the objective of his breeding program became: to create a hardy race or races of rhododendron that would include as many colors as possible, and extend the period of bloom both earlier and later into the season. Evidently in Germany, too, the day of the large estate had passed and a new style of house had come into fashion that required smaller and lower growing plants for landscape purposes. Hence small plants that would remain small for such homes were also to be sought. In the slides you will see for yourself how well Mr. Hobbie accomplished his objectives.
Now a few words about the breeding of his plants. (A fuller description of his program will form the subject of a separate paper to be submitted to the Bulletin ). Among the species he raised were rather fine and apparently hardy forms of R. williamsianum and R. forrestii var. repens . The first of these was used as the pollen parent for a large number of hybrids where the seed parent was a very hardy hybrid, in most cases one of the Seidel hybrids, but some of the species as well as some of the hardier Dutch and British hybrids were used too. From these crosses resulted offspring that formed dense, heavily foliaged plants, mound shaped, generally a little broader than high. Fifteen year old plants are three to five feet high. In general the colors are in shades of pink and rose; the trusses are mostly loose but borne in large numbers, some in over whelming quantities. Another interesting feature of this group of hybrids is the striking pink to orange to purplish brown color of the new growths that appear on many of the plants after the flowers have faded. A group of these plants makes a most impressive display that lasts for about two weeks before it changes to green.
From R. forrestii var. repens a large number of hybrids have resulted, the most important of which are R. 'Ursula Siems' (R. 'Earl of Athlone' x forrestii var. repens ), R. 'Gertrude Schale' (R. 'Prometheus' x forrestii var. repens ), R. 'Elizabeth Hobbie' (R. 'Essex Scarlet' x forrestii var. repens ) and R. 'Suomi' (R. 'Britannia' x forrestii var. repens ) x metternianum ). These are all dense, low growing plants bearing carmine or scarlet flowers. R. 'Suomi' is so called because it grows and blooms in Finland. It will be noted that here too the truss is lax and contains only a few flowers, but in many cases the number of trusses is so large that the foliage is practically concealed when the plant is in bloom.
Although group names are used for the crosses, Mr. Hobbie has selected the finest forms for clonal propagation and given these forms further identifying names. From an original three thousand plants of the R. 'Gertrude Schale' cross only six selected forms are being propagated. Similarly the R. 'Suomi' cross gave over fifteen hundred seedlings which have been reduced to about ten. In addition to hardiness one important criterion by which Mr. Hobbie selects his plants is that they should show no leaf burn in winter.
The slides we have seen are like a view of a factory where some magnificent product is manufactured, and should not be compared with a landscape planting in which the finest rhododendrons are assembled. Many of the seedlings shown in flower are inferior, undistinguished plants, and it is to be hoped that Herr Hobbie will soon destroy them. A very few showed evidence that they may be truly excellent varieties. If half a dozen out of all the thousands planted are eventually found to be outstanding, then Herr Hobbie's work will have proved a great success.
G. G. Nearing
Mr. Hobbie's hybridizing to create a new form of rhododendron is a trend in the right direction. The new design of the smaller house vetoes the large rampant type of rhododendron, and a dwarf compact rhododendron is to be sought. Since the climate of our Eastern seaboard is harsher than that of Mr. Hobbie's climate, it is only fair to allow at least three to five years trial here in our East to test the relative merits of this new race of rhododendron before passing judgment.
Comments on Hobbie's slides
We should not discount Hobbie's work on the basis of what we have seen tonight, because:
1) The photography (on Agfa film)
- made them appear unfavorable under artificial light
- made persistent bud scales too prominent
- distorted reds and greens
- had poor backgrounds and no scale of measurement.
2) The compact habit of the plants (for 50 weeks in the year) is a most important achievement irrespective of flower quality.
3) These are first-generation hybrids and can ultimately be greatly improved. These plants represent the basis for a new race of dwarfish compact plants that may become very important some time. The need of dwarf evergreen plants for landscape design cannot be overemphasized.
4) The red foliage of some of these hybrids is an interesting feature, recalling the same features in Pieris forrestii and west coast Vacciniums .
Comments on Hardiness
1) There are many factors besides temperature involved. Sometimes it is the ripening-off factor.
2) Some of the choicer British hybrids, not hardy here or in Germany, are not hardy in England, either, except in favored places, such as Cornwall, Wales and West Scotland.
Clement G. Bowers